This invention relates to seat assemblies for motor vehicles, and more particularly to a seat back frame for a vehicle seat assembly that includes reinforcement for resisting deflection caused by side impact loads.
Conventional seat backs for vehicle seats include a quadrilateral seat back frame. Structural integrity of such seat back flames is provided by vertical inboard and outboard members which are interconnected near their upper and lower ends by horizontally extending cross members and reinforced by gusset plates at the corners of the flame. Although this type of reinforcement provides a degree of rigidity to the seat back, it does prevent deflection of the seat back frame in response to a side impact, resulting in lateral distortion of the seat back, particularly under a high impact load. Because the vehicle seats are the primary means of support for the occupants of the vehicle, the lateral distortion of the seat caused by the deflection of the seat can result in injury to the occupant of the seat, particularly under high impact load conditions.
In U.S. Pat. No. 4,192,545, there is disclosed a vehicle seat back frame which is reinforced by a brace which extends diagonally from the lower end of the outboard side member to the upper end of the inboard side member. The diagonal brace is flexed or bowed in the rearward direction to provide clearance for the seat so that the cushioning property of the seat cushion is not impaired. Although this reinforcement arrangement provides resistance to lateral distortion under side loading conditions, the brace must straighten, resulting in dynamic loading of the brace as it is placed under tension during loading, before the brace is placed in tension and can take the load. Under extreme loads, the dynamic loading could result in a mechanical failure, permitting the seat to deflect or parallelogram. Because the seat is moving or deforming at the time that the tension member is placed in tension, there is dynamic loading which can cause breakage at stress points such as weld points, connections etc.